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Abstract

One of the most serious objections to the usual method of determining the water losses from plants is the almost universal use of containers which are quite too small to accommodate the normal development of the root system. But even where containers of sufficient size to overcome this obstacle are employed, the plants are grown in a mass of soil which has been at least fairly recently screened, mixed, aerated and watered and thus its structure is wholly unlike that which occurs in nature. This difference has been noticed for a number of years in connection with investigations of root systems of native and crop plants, as well as the markedly better growth of plants in the loose soil of trenches which have been refilled only one to four years. Just how long a time is required for such soil to assume the structure and take on the physical and chemical properties of that in an undisturbed area has not been determined, but casual observations indicate that many years are required. Undoubtedly the return to the former condition of equilibrium with surrounding soils, and the consequent effect upon the roots of plants, plays no small part in the phenomenon called plant succession, a process often requiring a minimum of 15-25 years for its completion.